1. Field of the Invention
The invention in general relates to the field of LTCC (low temperature cofired ceramic) circuitry.
2. Description of Related Art
An LTCC circuit is comprised of a plurality of ceramic layers with passive and/or active components and stacked together to form a module, with each ceramic layer containing thick film printed circuitry metallization, generally gold or silver. The ceramic layers include conductive vias for making electrical contact between layers and the ceramic layers are cofired at a temperature high enough to sinter the layers, yet low enough so as prevent flowing or melting of the metallization. The result of the firing is to form a rigid monolithic structure.
LTCC circuits have high packing density, can be customized to meet desired applications, are cost effective, reliable and can be controlled with respect to dielectric values. The LTCC allows for integration of digital and RF, stripline and microstrip circuits in a single light weight 3-D package. Such LTCC circuits are used for high frequency applications in both military as well as commercial devices.
In order to electrically connect the LTCC structure to other circuitry, wire or ribbon leads are bonded to conductors on the surface of the structure for connection to the other circuitry. A problem often arises however in that the bonded leads may form a poor contact with, or pull loose from, the conductors. This is due to the fact that the conductors contain one or more additives to promote conductor adhesion to the ceramic base layer and it is these additives which degrade the bonding of the leads.
It is therefore a primary object of the present invention to provide a low temperature co-fired ceramic (LTCC) structure with much improved lead bondability.